Structure-Based Drug Discovery Against the Caseinolytic Protease From Mycobacterium tuberculosis

Abstract

Antibacterial drug resistance is a major factor in the increasing rate of failure to successfully treat diseases such as tuberculosis (TB). The World Health Organization estimates that in 2015 a total of 10.4 million new cases of TB were diagnosed. Of which, 480,000 cases were resistant to standard first-line therapies - isoniazid and rifampicin – called multidrug-resistant TB (MDR-TB). A subtype of MDR-TB has resistance to more aggressive chemotherapy treatments that comprise the second line of TB drugs. This subtype is called extensively drug-resistant TB and constitutes 9.5% of MDR-TB diagnoses. Genomic studies of Mycobacterium tuberculosis (Mtb) - the causative agent of TB, have revealed a multitude of new targets for antibiotic therapies. One such target is the caseinolytic protease (ClpP1P2) and associated ATPase adaptors (ClpC1/X). The caseinolytic protease complex, ClpC1P1P2 is essential for maintaining proteostasis in Mtb via the degradation of misfolded and SsrA-tagged proteins identified by the ClpC1/X ATPase adaptor. Using biochemical methods and high throughput screening (HTS) technology we have characterized the inhibitory characteristics of thousands of compounds against the components of the caseinolytic protein complex. To complement this inhibition information, we grew crystals of the active ClpP1P2 protease. Future steps of this rational drug design project will include optimization and refinement of validation assays, as well as inhibitor soaking of ClpP1P2 crystals to resolve the binding of inhibitors on a molecular level. This information will be used to make rational refinements to the structure of inhibitors to increase their specificity, inhibitory characteristics and safety as therapies for the treatment of TB.